Lesson 3

Prior to this lesson, students made sense of tenths and hundredths in decimal notation. They also analyzed and wrote equivalent decimals. In this lesson, they use number lines to reason about the relative size of two or more decimals. The reasoning here is similar to that in an earlier unit, when students used number lines to compare fractions. Students see that, just as before, they can learn about the relative size of decimals by considering their positions on a number line and their relationship to benchmarks such as 0, 0.5, and 1. They will use these insights to compare and order fractions in the next lesson.

Students attend to precision and use the structure of the number line (MP6, MP7) when they locate and label decimals between two tick marks representing tenths. For example, halfway between 0.4 and 0.5 will be the decimal 0.45 whereas 0.48 will be much closer to 0.5 than to 0.4.

Activity 1: Points on Number Lines